1. Field of the Invention
The present invention relates to pressure sensing, and particularly to a tire pressure control system.
2. Description of the Related Art
Air pressure buildup in the tires of vehicles, such as motorsports vehicles, has been a problem. Tires, such as tires used for motorsports vehicles, will perform noticeably and dramatically different as the air pressure changes. For example, pressure changes of as little as tenths of a pound per square inch (PSI) can cause the performance of tires to change.
In certain situations, air pressure changes can also be utilized. For example, a different air pressure can be utilized for changing surface conditions to enhance the grip of the tire to the surface. Another example can be in changing the set-up of the vehicle, in which a certain tire on the vehicle can grip more or less than the other tires in order to make the vehicle turn more or less, depending on surface conditions. This can result in different optimum pressure from tire to tire.
Various approaches commonly used today attempt to address and combat problems with air pressure. One approach is to start an event with less pressure in the tire than is best suited for the tires optimum performance pressure. This is done in order to guess at how much pressure the tire will gain to attain its optimum performance pressure once it reaches its highest temperature under race conditions. This approach can be problematic, due to the poor performance at the start of an event with the lower air pressure, and that it is merely a guess as to how much pressure gain will occur.
Another approach is to use compressed nitrogen, since nitrogen will not gain as much pressure under heat changes as regular compressed air. However, with this approach, a user must purge the air out of the tire by filling the tire with nitrogen, and also by using a suction or vacuum device to evacuate all of the air they can. Then, you need to refill the tire with compressed nitrogen, and you have to repeat this step several times to evacuate as much of the compressed air as possible. Under this approach you can never remove all of the compressed air, and then the nitrogen still has some pressure gain when the tire increases the temperature under race conditions, once again guessing to attain the proper pressure setting.
Another way, which can be considered the most common in motorsports today, is the use of a manual pop off bleeder valve. These manual pop-off bleeder valves on the market today generally consist of a unit, that has a body, and that contains a diaphragm seat. The diaphragm seat is preset with the pressure of a spring, which is adjusted by the height of the spring retainer, which puts more or less pressure on the seats as to bleed off the air at a preset pressure. The diaphragm seat is then connected to the wheel via a quick connect hub that access the tire's pressure.
While these approaches may help, there are still many problems with them. One of the possible problems involves the diaphragms, which can be very small. Further, the bleed off in many instances is slower than the pressure buildup. For example, you may want the bleeder to maintain 8 psi, and sometimes it may not start bleeding aggressively until closer to 9 psi. So it takes a longer period of time to bleed down to the preferred 8 psi because as the pressure gets closer to the preferred 8 psi, the bleed off becomes slower due to less pressure against the spring so the diaphragm isn't opened as much.
To compensate for this problem, you then set the bleeder pop off to a lower than desired pressure to help keep up with the pressure buildup. However, this also has its problems as to the fact that you must start the event with less than desired pressure as to maintain the preferred operating pressure during race conditions. But then during the event there may be a caution period in order to assist in a wreck of another vehicle. At idle speed the bleeder will bleed the tire pressure off back to the lower pressure, thus making the tire not perform at the optimum performance once the race resumes.
Many times these bleeders have a tendency to stick open when debris gets in the diaphragm. Or, the diaphragms gets overused, sometimes resulting in a flat tire which then has to be changed to a new tire, thus taking you out of the competition. It is not unusual to spend thirty minutes or more working on each of these bleeders each time you reset them to a different pressure or simply to maintain the current pressure setting for they are not very repetitive.
Bleeder valves have been utilized in motorsports vehicle pneumatic tires for years as a way to bleed off excess tire pressure buildup due to heat gain under race conditions. One such example of this device was awarded to Worth, in U.S. Pat. No. 5,257,642. In this patent, a mechanical device is mounted into the wheel of the tire/wheel assembly, with a spring-actuated diaphragm that is preset to an upper limit, to release excess tire pressure buildup due to heat gain inside the tire. This unit takes several minutes to change the setting and still isn't very accurate to precise settings, and doesn't repeat consistently.
Another example of these types of devices was awarded to Conroy Sr. in U.S. Pat. No. 5,954,084. This device is also a spring-actuated diaphragm that is located in the central axis of the axle of the wheel/tire assembly, so as to alleviate the rotating centrifugal force on the mechanical device, like the above mentioned device by Worth. Although this device does tend to operate better because it utilizes a larger diaphragm, it is still a mechanical device that has the same problems with precision, repeatability and consumption of time when presetting the device.
Another device is a pressure control system that was awarded to Wilson in U.S. Pat. No. 7,690,411. This device is mounted to the wheel and utilizes a servo mechanically connected to a valve that can release or add pressure to a tire, which is in direct control of the driver of the vehicle, which also utilizes a pressurized tank that is mounted in the axle of the wheel/tire assembly for adding air pressure when needed. The problems with such a device are that it is mounted directly to the wheel. Further, the use of a mechanically operated valve can need extra maintenance, and that it must be mounted to each individual wheel and by not mounting the device in the center of the rotating axis of the wheel/tire assembly. Additionally, the assembly will have to be balanced to accommodate the device, thus adding unwanted rotating weight to the wheel/tire assembly, which is a drain on the vehicles engine power.
Therefore, it is desirable for a method and apparatus that allows for digital pressure regulating that is easy to setup, install and/or change the pressure amount by hundredths of a pound (psi) quickly in vehicles, such as motorsports vehicles, and the like. It is further desirable for all these various features to be implemented within a single apparatus for easy use and maintenance, so that it can easily be quickly removed when changing the tire/wheel or for maintenance when need be. Additionally, it is also desirable for the apparatus to be capable of moving from one wheel to another, or to be removed from the wheel, in a hurried situation.
Thus, a tire pressure control system addressing the aforementioned problems is desired.